ENGINE LIMITATIONS
ENGINE INTERMEDIATE LIMITATIONS
Engine intermediate limitations –ie maximum continuous (AEO and OEI),
take off power rating (AEO) and 2.5-minute power rating (OEI) for Ng, ITT
and Tq– are intended to protect engine life only. The EEC does not provide
any automatic control to respect such limits, nor any time limits; it is then
pilot’s responsibility not to exceed engine limits.
When operating in the OEI 2.5 minute rating range for either Ng, ITT or Tq,
the 2.5 min annunciator is displayed in steady amber normal video on the
left/right side of PI indicator (on-side with the operating engine) on the PFD
and between the NG and the ITT indicators on the MFD Pwr Plant page.
This annunciators change into blinking red inverse video when within 10
seconds of exceeding the OEI 2.5-minute time limit.
In case the OEI 2.5-minute rating is exceeded, the 2.5 min annunciators are
displayed in steady red inverse video and the 1(2) ENG LIM EXPIRE caution
is displayed in the CAS.
EEC LIMITING FUNCTIONS
The EEC controls the engine parameters to provide protection for the
engines and transmission in AEO, OEI and OEI TNG conditions.
The limiting function of the EEC control takes effect when the first limit
reaches the maximum allowable value by stopping the fuel demand, thus
permitting a rotor droop to occur.
Ng and ITT maximum allowable values (or maximum transient values) are
indicated by red triangles on Ng and ITT scales; ITT maximum starting limit
is indicated by a red half circle on the ITT scale, on-side with the engine
being started.
Maximum allowable local torque value is 160%. A pilot selectable Torque
Limiter Function permits the AEO total torque to be limited to 114% per
engine.
Engine is also protected against Nf overspeed by an independent Nf
Overspeed Protection circuit.
TORQUE LIMITS AND TORQUE LIMITER
EEC limits local torque to a maximum allowable value of 160%, which could
result in a total AEO power of 320% Tq applied to the transmission.
Engine AEO power can be automatically limited by the EEC in order to
protect the main gearbox by engaging the Torque Limiter function. This is
achieved by pressing the TQ LIM pushbutton on the collective grip; when
pressed the EECs control the total engine torque in order not to exceed
228% of total torque (114% per engine).
The Torque Limiter function is not available in single engine operation.
When Torque Limiter is engaged, the TQ LIMITER ON advisory message is
displayed in the CAS. If the Torque Limiter function fails, the 1(2) TQ
LIMITER caution message is displayed in the CAS.
Torque is the only parameter involved in the limitation: Ng and ITT could
reach the single engine limits even in AEO with TQ LIM engaged, if dictated
by the environmental conditions.
Torque limitation is not available in MANUAL mode.
At power-up the Torque Limiter is OFF by default: it is therefore pilot’s choice
to manually engage it.